Low-power radio transmitter shrinks to 3mm square

Microelectronics International

ISSN: 1356-5362

Article publication date: 1 April 2005




(2005), "Low-power radio transmitter shrinks to 3mm square", Microelectronics International, Vol. 22 No. 1. https://doi.org/10.1108/mi.2005.21822aad.008



Emerald Group Publishing Limited

Copyright © 2005, Emerald Group Publishing Limited

Low-power radio transmitter shrinks to 3mm square

Low-power radio transmitter shrinks to 3mm square

Keywords: Radio transmitters

The MAX1479 is the world's smallest VHF/UHF PLL-based ASK/FSK transmitter to deliver more than +10 dBm output. It is housed in a small, 3×3 mm, 16-pin thin QFN package. This transmitter is perfect for low-cost, high-volume applications where space is critical, such as tyre pressure monitoring systems (TPMS), keyfobs, security products, garage door openers, and remote sensors operating in the 300-450 MHz band.

The MAX1479 has a simple data interface and a divider-programmable clock-out feature that eliminates the need for an MCU resonator. The MAX1479 is designed to run directly off a lithium cell, and will operate down to 2.1 V, consuming only 0.2 nA of current in standby mode. The output power of the MAX1479 can be adjusted from -10 to +10 dBm into a 50 Ω load by using an external resistor. At the +10 dBm power level, the MAX1479 consumes 6.7 mA of current at 315 MHz when using a 50 per cent duty-cycle encoding scheme, such as Manchester. Current consumption is only 4.5 mA at 0dBm output. The part can transmit at date rates up to 100 kbit/s in ASK and 20 kbit/s in FSK (both Manchester encoded). Once the enable pin of the MAX1479 is activated, it takes only 200 ms for the PLL and crystal to settle and be available to transmit.

As the device is targeted at small, portable applications, the MAX1479 accepts crystal frequencies from 9 to 15 MHz, widely available in inexpensive, surface-mount packages. Further, Maxim has established relationships with crystal suppliers who can provide reference samples of crystals on request. Because the MAX1479 uses a crystal-based PLL, most of the problems of an LC or SAW- based transmitter are eliminated. The inherent accuracy of the crystal frequency allows a narrower IF bandwidth in the receiver to improve system sensitivity. Used with a receiver like Maxim's MAX1470, MAX1471 or MAX1473, the MAX1479 transmitter can improve overall system sensitivity, 9 dB, simply by narrowing the IF bandwidth from 600 to 50 kHz. Improved sensitivity translates directly to greater range or more reliable transmissions. The MAX1479 operates over the automotive temperature range (-40 to +125°C). Prices start at $0.99 (10,000-up, FOB USA). Evaluation kits are available to speed designs.

For more information, contact E-mail: jvanzandt@maxim-ic.com

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